1. Field of the Invention
The present invention relates to a wireless network system and a method for transmitting and receiving data over the wireless network system, and, more particularly, to a wireless network system, in which time periods for a bandwidth allocation request and a bandwidth-allocation-acknowledge packet are separately set within a superframe and data is transmitted or received in allocated bandwidths, and a method of transmitting and receiving data over the wireless network system.
2. Description of the Related Art
FIG. 1 is a view illustrating the structure of a related art superframe. As illustrated in FIG. 1, the related art superframe 100 is composed of a beacon period 110 appearing in the starting portion thereof, a Contention Access Period (CAP) 120, and Channel Time Allocation Period (CTAP) 130. During the CAP 120, asynchronous data, control commands, or the like can be transmitted or received. The CTAP 130 consists of a plurality of blocks of Management Channel Time Allocation (MCTA) 131 and a plurality of blocks of Channel Time Allocation (CTA) 132. Control commands, isochronous data, asynchronous, or the like can be transmitted or received through the CTA 132.
The length of the CAP 120 is determined by an Access Point (AP), and transmitted to stations participating in a network through a beacon frame distributed in the beacon period 110.
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is used in the CAP 120 for media access. In contrast, Time Division Multiple Access (TDMA) during which each wireless network station has a specific time window is used in the CTAP 130. An AP allocates a channel time to a device requesting media access, and performs transmission or reception of data with a corresponding wireless network station during the allocated channel time. Here, the MCTA 131 is assigned to a pair of wireless network stations attempting to exchange data, so that it performs media access through a TDMA media access, or is used as a shared CTA using the slotted Aloha protocol.
There are two data transmission schemes: a compressed data transmission mode; and an uncompressed data transmission scheme. In the first transmission mode, compressed data is transmitted through a bandwidth of several gigabytes. In the latter transmission mode, uncompressed data is transmitted through a bandwidth of several tens of gigabytes. The uncompressed data, which is larger than the compressed data, can be transmitted through a bandwidth of several tens of gigabytes. Uncompressed data is less vulnerable to packet loss occurring during data transmission than in the case of compressed data. In order for a transmitting station to transmit data, the transmitting station should send a request for bandwidth allocation and then receive an acknowledgement response. This procedure is made in the CAP 120. That is, the transmitting station should contend with other stations existing on the network for media access. Here, when the transmitting station cannot receive the acknowledgement for the bandwidth allocation in the media access contention, the transmitting station has to wait for a next contention period or a next superframe.
For these reasons, a receiving-station user who attempts to receive multimedia content from the transmitting station for real-time reproduction may encounter inconvenience due to a delay in data reception. Accordingly, a method of effectively transmitting and receiving data through an improved contention mechanism is needed.